1. Field of the Invention
The invention relates to a light guide module, and more particularly, to a light guide module of a keyboard, manufacturing method thereof, and a backlit keyboard having the light guide module.
2. Description of the Prior Art
Backlight module is essential to a display or a luminous electronic device like a backlit keyboard, and the light guide plate is one of the key components of the backlight module. To allow more light projected from the backlight module, a reflecting layer is a common solution, which is disposed at a side of the light guide plate opposite to the light-exit surface. The light reflected from the light-exit surface may be further reflected by the reflecting layer back into the light guide plate and the light usage can be increased. Generally, metal has higher reflecting rate and is a suitable material for the reflecting layer. However, with the trend of building the electronic devices in a much lighter and thinner way, it is an inevitable problem that the electromagnetic interference (EMI) should be taken into consideration when using metal as the reflecting layer.
Take a backlit keyboard as an example, a backlit keyboard generally has a light guide plate disposed between a keyswitch module and a circuit unit, whereas a metal reflecting layer is disposed between a light guide plate and the circuit unit. However, as the backlit keyboard is in use, the metal reflecting layer not just reflects the light from the light guide plate, the metal reflecting layer further becomes a medium for conveying electromagnetic waves due to the conductivity of the metal layer. Such characteristic produces abnormal reflection of electromagnetic waves and causes instability to the system.
Additionally, since the metal reflecting layer is conductive, short circuit is likely to happen between the reflecting layer and the circuit unit below, which seriously injures the performance of the device. Hence, it is essential to prevent unwanted interference between the metal reflecting layer and the circuit unit, while the electromagnetic interference is expected to be reduced.